Patent Application
20120039268
The present invention generally relates to wireless communication. In particular, the present invention relates to apparatuses, methods and computer programs operating in wireless communication systems and/or controlling wireless communication systems as well as to systems comprising such apparatuses and computer programs which may be operated and/or controlled by such methods and computer programs.
Specifically, non-limiting embodiments of the present invention relate to the LTE/E-UTRAN Downlink and Uplink air interface and its evolution towards further releases (i.e. LTE-Advanced) and may be applied to any other OFDM or any other transmission technology.
For the description set forth hereinafter, the following abbreviations are defined:
3GPP 3rd Generation Partnership Project
ARQ Automatic Repeat Request
DL Downlink
eNB evolved Node B
E-UTRAN Evolved UTRAN system
ICIC Inter-Cell Interference Coordination
LTE Long Term Evolution of UTRAN system
LTE Rel-8 LTE release 8
OFDM Orthogonal Frequency Division Multiplex
PBCH Physical Broadcast Channel
PCFICH Physical Format Indicator Channel
PDCCH Physical Downlink Control Channel
PDSCH Physical Downlink Shared Channel
PHICH Physical Hybrid ARQ Indicator Channel
PMCH Physical Multicast Channel
PRACH Physical Random Access Channel
PUCCH Physical Uplink Control Channel
PUSCH Physical Uplink Shared Channel
RRC Radio Resource Control
SC sub-carrier
TTI Transmission Time Interval
UE User Equipment
UL Uplink
UMTS Universal Mobile Telecommunications System
UTRAN UMTS Terrestrial Radio Access Network
Related prior art can be found e.g. in the technical specifications of the 3GPP, namely documents TS 36.101 (v8.4.0), TS 36.104 (v8.4.0), TS 36.211 (v8.5.0), TS 36.212 (v8.5.0), TS 36.213 (v8.5.0), and TS 36.331 (v8.4.0), all related to release 8 and hereinafter referred to in the form of “TS 36.101”, etc.
According to this prior art, the LTE/E-UTRAN Downlink air interface (see TS 36.211, TS 36.212, and TS 36.213) is based on Orthogonal Frequency Division Multiple Access comprising the following data channels: Physical Downlink Shared Channel (PDSCH) and Physical Multicast Channel (PMCH), as well as on the following control channels: Physical Downlink Control Channel (PDCCH), Physical Control Format Indicator Channel (PCFICH), Physical Hybrid Indicator Channel (PHICH), Physical Broadcast Channel (PBCH), and Primary and secondary synchronization channel (SCH).
For LTE Rel-8 system bandwidths larger than 1.4 MHz, 1, 2, or 3 OFDM symbols per TTI can be configured for the PDCCH channel. The number of PDDCH OFDM symbols depends on the traffic model, i.e. on the amount of user equipment scheduled (both in Downlink and in Uplink) in the corresponding TTI.
The LTE/E-UTRAN Uplink air interface (see TS 36.211, TS 36.212, and TS 36.213) is based on Single Carrier Frequency Division Multiple Access (SC-FDMA) comprising the following shared channel: Physical Uplink Shared Channel (PUSCH) and the following physical control channels: Physical Uplink Control Channel (PUCCH) and the Physical Random Access Channel (PRACH).
At present, the PUCCH resource pool can be configured symmetrically with respect to the carrier center at the lower and upper carrier edges. The PUCCH is hopping with a hopping frequency of TTI (=1 time slot).
The mapping of logical resource blocks (denoted as m) into physical resource blocks is shown in
Currently, an asymmetric (with respect to the carrier center) PUCCH resource pool configuration is discussed in 3GPP.
The PRACH channel can be configured anywhere in the Uplink spectrum. The following further denotations apply:
The first physical resource block nPRBRA allocated to the PRACH opportunity is defined as nPRBRA=nPRB offsetRA, where the PRACH frequency offset nPRB offsetRA is expressed as a physical resource block number configured by higher layers and fulfilling 0≦nPRBoffsetRA≦NRBUL−6.
The resource mapping of the physical Downlink and Uplink channels relates to the Downlink N_DL_RB and Uplink system bandwidth N_UL_RB which are configuration parameters in the TS 36.21x specifications and which represent the available number of Downlink or Uplink Resource Blocks (RBs).
While the PBCH and the Primary and Secondary SCH are centered with respect to the DL carrier using a narrow bandwidth of 6 Resource Blocks (RBs), the PDCCH, the PCFICH and the PHICH extend over the complete Downlink system bandwidth as configured by N_DL_RB. The PDSCH and the PMCH allocations are controlled by scheduling. Further limitation of PDSCH and PMCH bandwidth beyond the configuration limit N_DL_RB depends on the DL scheduler and is LTE Rel-8 compliant.
Further limitation, however, of the PDCCH, PCFICH, and PHICH beyond the configured Downlink system bandwidth is not possible in general and may require an optimized control channel DL scheduler.
While the PRACH can be configured anywhere, and the PUSCH can be limited in bandwidth beyond the configuration limits set by N_UL_RB, the PUCCH resource pool exactly exploits the configured N_UL_RB.
Hence, further limitation of UL bandwidth beyond the configured Uplink system bandwidth is not possible in general or may require an optimized control channel UL scheduler.
The LTE system bandwidths could be flexibly configured if all options for N_DL_RB and N_UL_RB ranging from 6 RBs up to 110 RBs are supported.
However, following TS 36.104 and TS 36.101 only selected LTE system bandwidths N_RB are supported by the standard Rel-8: For frequency division duplexing (FDD) these are 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz and 20 MHz. The standardized system bandwidths are given e.g. in Table 5.6-1 of version 8.4.0 of TS 36.104 (analogous in TS 36.101) which is shown in
The RRC layer sets the Downlink and Uplink system bandwidths in the Master and System Information Blocks as specified in TS 36.331. The supported bandwidths (for Downlink and Uplink independent values) correspond to the ones listed in Table 5.6-1 of TS 36.104 shown in
In accordance to the aforementioned, in LTE Rel-8 a deviation from the configured Downlink and Uplink system bandwidths is not possible in general.
Hence, the strict limitation of LTE Downlink and Uplink system bandwidths leads to limitations in spectrum exploitation.
Specifically, operators having spectrum blocks not matching the configurable system bandwidths cannot fully exploit their spectrum. They should use the next smaller system bandwidth (e.g. 5 MHz in a 9 MHz frequency block) or retreat to a multi-carrier LTE system where a set of smaller bandwidths is used to exploit the operator's spectrum.
In future LTE releases (e.g. LTE-Advanced), carrier aggregation will be a key feature. However, with the limited set of LTE Release 8 bandwidths also the contiguous or non-contiguous aggregation of the carriers will suffer from limitations for spectrum exploitation.
Operators having spectrum blocks not matching the configurable system bandwidths may thus combine multiple smaller carriers for a multi-carrier LTE network (e.g. 5+3 MHz in a 9 MHz frequency block), or squeeze a 10 MHz system bandwidth into 9 MHz.
The former solution does not fully exploit the available spectrum, while the latter solution can only be used if the deviation from the configurable DL system bandwidth is not too large and if the coexistence situation allows for using standard terminals (e.g. in this case at 10 MHz).
In the light of the above, it is an object of the present invention to overcome the shortcomings of the prior art.
According to a first aspect of the present invention there is provided an apparatus, comprising a carrier utilization element configured to utilize a combination of pre-configured channel bandwidths for wireless communication within an available frequency spectrum, wherein the combination includes overlapping pre-configured channel bandwidths.
The first aspect of the present invention may be modified as follows.
The apparatus may be suitable for optimizing spectrum exploitation.
Carriers corresponding to the overlapping pre-configured channel bandwidths may comprise a time offset.
The apparatus may further comprise a downlink scheduler element configured to avoid allocation of a downlink data channel in a region of overlapping pre-configured channel bandwidths.
Outer guard bands for the available frequency spectrum in which no channels are to be allocated may be provided by virtual guard bands of the pre-configured channel bandwidths.
The downlink scheduler element may be further configured to send cell-specific downlink reference symbols of both of the carriers corresponding to pair-wise overlapping pre-configured channel bandwidths in the region of overlapping pre-configured channel bandwidths.
The apparatus may be configured as a user equipment component and the carrier utilization element may be further configured to utilize the overlapping pre-configured channel bandwidths at the same time.
The apparatus may be configured as a base station and the carrier utilization element may be further configured to schedule the overlapping pre-configured channel bandwidths for use at the same time.
According a second aspect of the present invention, there is provided a method, comprising utilizing a combination of pre-configured channel bandwidths for wireless communication by a carrier utilization element within an available frequency spectrum, wherein the combination includes overlapping pre-configured channel bandwidths.
The second aspect of the present invention may be modified as follows.
The method may be suitable for optimizing spectrum exploitation.
Carriers corresponding to the overlapping pre-configured channel bandwidths may comprise a time offset.
The method may further comprise avoiding allocation of a downlink data channel in a region of overlapping pre-configured channel bandwidths by a downlink scheduler element.
Outer guard bands for the available frequency spectrum in which no channels are to be allocated may be provided by virtual guard bands of the pre-configured channel bandwidths.
The method may further comprise sending cell-specific downlink reference symbols of both of the carriers corresponding to pair-wise overlapping pre-configured channel bandwidths in the region of overlapping pre-configured channel bandwidths by the downlink scheduler element.
The method may further comprise utilizing the overlapping pre-configured channel bandwidths at the same time by a user equipment component.
The method may further comprise scheduling the overlapping pre-configured channel bandwidths for use at the same time by a base station.
According to a third aspect of the present invention, there is provided a computer program product embodied on a computer-readable medium encoded with instructions that, when executed on a computer, perform utilizing a combination of pre-configured channel bandwidths for wireless communication by a carrier utilization element within an available frequency spectrum, wherein the combination includes overlapping pre-configured channel bandwidths.
The third aspect of the present invention may be modified in a manner corresponding to the modifications of the second aspect.
According to a fourth aspect of the present invention, there is provided a system, comprising one or more power amplifier configured to provide at least two carrier having overlapping channel bandwidths; and a cellular wireless communication network controller configured to provide an air interface communication protocol over a range covered by the overlapping channel bandwidth.
The fourth aspect of the present invention may be modified as follows.
The system may be suitable for optimizing spectrum exploitation.
The system may further comprise a deployment element configured to deploy one of a set of combinations of pre-configured channel bandwidths, in which for each combination the carrier center frequency of each pre-configured channel bandwidth comprises the same distance to a lower edge of an available frequency spectrum, for a specific cell of the cellular network, and to deploy another one of the set of combinations for a cell neighboring to said specific cell.
According to a fifth aspect of the present invention, there is provided an apparatus, comprising a means for utilizing a combination of pre-configured channel bandwidths for wireless communication within an available frequency spectrum, wherein the combination includes overlapping pre-configured channel bandwidths.
The fifth aspect of the present invention may be modified in a manner corresponding to the modifications of the first aspect.
According to a sixth aspect of the present invention, there is provided a system, comprising one or more power amplifier means for providing at least two carrier having overlapping channel bandwidths; and a cellular wireless communication network controlling means for providing an air interface communication protocol over a range covered by the overlapping channel bandwidth.
The sixth aspect of the present invention may be modified in a manner corresponding to the modifications of the fourth aspect.
According to a seventh aspect of the present invention, there is provided a method, providing at least two carriers having overlapping channel bandwidths by one or more power amplifier; and providing an air interface communication protocol over a range covered by the overlapping channel bandwidth by a cellular wireless communication network controller.
The seventh aspect of the present invention may be modified as follows.
The method may be suitable for optimizing spectrum exploitation.
The method may further comprise deploying one of a set of combinations of pre-configured channel bandwidths by a deployment element, in which for each combination the carrier center frequency of each pre-configured channel bandwidth comprises the same distance to a lower edge of an available frequency spectrum, for a specific cell of the cellular network, and deploying another one of the set of combinations for a cell neighboring to said specific cell by said deployment element.
Other objects, features and advantages of the present invention will become apparent from the following detailed description of the embodiments of the present invention which is to be taken in conjunction with the drawings, in which:
a shows varying Frequency Reuse >1 schemes for frequency blocks not matching LTE Rel-8 bandwidths according to an embodiment of the present invention; and
b shows varying Frequency Reuse >1 schemes for frequency blocks not matching LTE Rel-8 bandwidths according to another embodiment of the present invention.
In the following, description will be made to what are presently considered to be preferred embodiments of the present invention. It is to be understood, however, that the description is given by way of example only, and that the described embodiments are by no means to be understood as limiting the present invention thereto.
For example, for illustration purposes, in the following exemplary embodiments are described inter alia with respect to LTE/E-UTRAN. However, it should be appreciated that these exemplary embodiments are not limited for use among this particular type of wireless communication systems, and according to further exemplary embodiments, the present invention can be applied to other communication systems where it is possible that the configurable system bandwidths do not match the frequency spectrum block for operation. Thus, it should be apparent that still further exemplary embodiments are related to optimized spectrum exploitation in other communication systems.
According to certain embodiments of the present invention, a given frequency spectrum block for operation is exploited in a more optimized way by a combination of multiple overlapped carriers which overlap with respect to the configurable standard system bandwidth both for LTE Release 8 as well as for future LTE releases (e.g. LTE-Advanced) and which increase the possibilities to enhance Inter-Cell Interference Coordination (ICIC) schemes as an example for network optimization.
For example, for LTE Rel-8, two of the 5 MHz configured system bandwidths can be used in overlapped fashion for a 9 or 9.2 MHz spectrum (typical GSM re-framing remainder).
Further, for LTE-Advanced, e.g. a 20 or (2×10) MHz configured system bandwidth plus a 10 MHz configured system bandwidth can be used in overlapped fashion for a 28 MHz spectrum to be LTE Rel-8 backward compliant (4×7 MHz blocks in WiMAX band).
Accordingly, the overlapped carriers may be
Overlapped carriers can be exploited to enhance the degrees of freedom for network optimization for example for Inter-Cell Interference Coordination (ICIC).
Referring e.g. to the above example based on a 9 MHz frequency block, an operator may deploy a Frequency Reuse >1 scheme for Inter-Cell Interference Coordination which consists of the following three cell deployment variants:
This is a set of multi-carrier schemes which maintains the carrier center positions (enabling intra-frequency handover for ease of implementation as well as handover optimization) and leaves varying parts of the shared channel unallocated such that an ICIC scheme can be applied.
In the following, certain embodiments of the present invention are described in greater detail in order to illustrate the obtainable advantages and technical possibilities even further.
As indicated above, according to certain embodiments of the present invention the overlapped carriers can be used for optimum spectrum exploitation. This is described hereinafter in further detail.
The concept of overlapped carriers for LTE Rel-8 and backward-compliant with LTE Rel-8 can comprise the following.
The eNB is synchronized to the level of OFDM symbols with a synchronization spread significantly less than the propagation delay spread.
Two or more carriers may be transmitted from a single power amplifier or multiple power amplifiers as follows: The center frequencies of these carriers and the standard configurable bandwidth of these carriers are defined in such a way that the overall bandwidth covered by the combined multiple carriers matches the spectrum bandwidth available to the operator. In the example used so far, this corresponds in allocating two 5 MHz carriers with a 3.9 MHz distance between the center frequencies to cover close to 9 MHz.
This is illustrated in
Specifically, according to certain embodiments of the present invention, the following Downlink coordination steps can be applied in case of overlapped carriers:
Uplink interference coordination for overlapped carriers exploits a PUCCH blanking technique. Based on LTE release 8, PUCCH Blanking refers the following: The PUCCH resource pool in multiples of Physical Resource Blocks (PRBs) is overdimensioned first, then outer PRBs of the PUCCH resource pool are not used for PUCCH allocation.
Finally, depending on the available UL bandwidth, the UL scheduler may allocate the PUSCH channel onto unused PUCCH resources.
In contrast to the Downlink, in Uplink the overlap area is allocated to one of the overlapping carriers.
According to certain embodiments of the present invention, considerable resource gains from are obtained by the LTE Rel-8 overlapped carrier deployment.
In order to illustrate the potential of overlapped carrier deployment, in the following table resource gains for an overlapped carrier deployment are compared to a conservative multiple carrier deployment with (one) smaller bandwidth(s).
As mentioned above, according to certain embodiments of the present invention an ICIC network optimization is enabled by exploiting the overlapped carrier deployment. This is described hereinafter in further detail.
a and 5b illustrate for various frequency blocks not matching the LTE Rel-8 bandwidths potential dual-carrier deployments that allow for Inter-Cell Interference Coordination.
In those deployment variations using overlapped carriers, the non-allocation of the downlink channels in the overlapped area and the allocation of the uplink channels in the overlapped area are indicated by hatching in the same manner as in
As explained above for the example based on a 9 MHz frequency block, an operator may deploy a Frequency Reuse >1 scheme for Inter-Cell Interference Coordination which consists of the following three cell deployment variants:
This is an example for a dual-carrier scheme based on overlapped carriers which maintains the carrier center positions (enabling intra-frequency handover for ease of implementation as well as handover optimization) and leaves varying parts of the frequency block unallocated such that a static ICIC scheme can be applied.
Those embodiments of the present invention which include the dual-carrier ICIC scenarios based on overlapped carriers comprise the following advantages:
As mentioned above, certain embodiments of the present invention are related to aggregating overlapped carriers, for example in LTE-Advanced. This is described hereinafter in further detail.
That is, both Downlink and Uplink interference coordination for overlapped carriers can be of great advantage in future LTE releases, namely in the LTE-Advanced system. In 3GPP, it is widely agreed that an LTE Rel-8 backward compatible approach to providing more than 20 MHz bandwidth consists of aggregating 20 MHz and 10 MHz LTE Rel-8 carriers in an LTE-Advanced super channel structure.
In order to understand the benefits of the overlapped carrier concept for LTE-Advanced, an example of deploying 2×6 MHz carriers in a 12 MHz frequency block—which is typical in 2.6 GHz frequency bands—is studied in the following. Currently, there are basically three different methods for LTE-Advanced carrier aggregation discussed:
While carrier aggregation in LTE-Advanced for non-overlapping carriers (see Table 2) requires bandwidth extension for LTE Release 8 backward compatibility on the one hand and standardization of RF requirements for new bandwidths (like 6 MHz in this example) on the other hand, using the overlapped aggregated carriers (see Table 3) enables LTE Release 8 backward compatibility directly. Also, the complete bandwidth is open for LTE Release 8 backward compatibility allowing for a higher amount of low-end mobiles also in an LTE-Advanced system.
That is, using the contiguous carrier aggregation concept for a 12 (2×6) MHz frequency block, the following possibilities exist:
Certain embodiments of the present invention also include the following.
In an enhanced system such as e.g. the LTE-Advanced release of the 3GPP LTE standard selecting, combining, coordinating, and scheduling overlapping pre-configured channel bandwidths is applied to aggregated channels (or Component Carriers).
As aggregated channels (or Component Carriers) refer to a system enhancement where the user equipment uses these channels at the same time, these embodiments also comprise that the concept of overlapping carriers is applied to user equipment where overlapped pre-configured channel bandwidths are used at the same time.
As aggregated channels (or Component Carriers) also refer to a system where the base station performs scheduling decisions for various component carrier aggregation options, these embodiments also comprise that the base station can schedule in such a way that the user equipment can use overlapped pre-configured channel bandwidths at the same time. It is to be understood that a base station may also be a Node B and an evolved Node B, respectively.
According to the above description, it should be apparent that exemplary embodiments of the present invention provide, for example from the perspective of a base station such as an evolved Node B (eNB) or from the perspective of a user equipment, or a component thereof, an apparatus embodying the same, a method for controlling and/or operating the same, and computer program(s) controlling and/or operating the same as well as mediums carrying such computer program(s) and forming computer program product(s). The exemplary embodiments of the present invention particularly also include any combination of the above described features unless explicitly described to be technically contrary or exclusively alternative.
For example, described above are apparatuses, methods and computer program products capable of optimizing spectrum exploitation and network optimization e.g. by providing overlapped carriers.
Implementations of any of the above described blocks, apparatuses, systems, techniques or methods include, as non limiting examples, implementations as hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.
What is described above is what is presently considered to be preferred embodiments of the present invention. However, as is apparent to the skilled reader, these are provided for illustrative purposes only and are in no way intended that the present invention is restricted thereto. Rather, it is the intention that all variations and modifications be included which fall within the spirit and scope of the appended claims.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2009/051464 | 2/9/2009 | WO | 00 | 10/31/2011 |
